Properties of Sulfonated Poly(Arylene Ether Sulfone)/Functionalized Carbon Nanotube Composite Membrane for High Temperature PEMFCs

Composite membranes are prepared using sulfonated poly (arylene ether sulfone) (SPAES) copolymers and the incorporation of functionalized multiwall carbon nanotubes (CNTs) for high temperature (120 degrees C) proton exchange membrane fuel cells (PEMFCs). The CNT is functionalized with sulfonated groups that are expected to support the improvement of water absorption and mechanical properties. The SPAES copolymers are synthesized with sulfonation degree (DS)=0.5 and the sulfonated CNT (s-CNT) is dispersed into the SPAES copolymers in varying ratios to fabricate the composite membranes. In this study, the proton conductivity, water uptake, and single cell test of the composite membrane are investigated for verifying the effects of the enhancement at high temperature and low humidity. The composite membrane containing 0.2wt.% s-CNT increases proton conductivity approximately 45% at 120 degrees C and 50% relative humidity and enhances the tensile strength by about 1.3 times compared to the pristine membrane. However, the proton conductivity and water absorption shows a decline when more than 0.2wt.% s-CNT is added in the composite membrane, due to the aggregation of the s-CNT, which serves as a proton barrier. For the single cell test, the developed composite membrane with 0.2wt.% s-CNT exhibits a notable performance for high temperature PEMFC.